feud vs go to war

feud

verb
  • To carry on a feud. 

noun
  • A state of long-standing mutual hostility. 

  • An estate granted to a vassal by a feudal lord in exchange for service. 

  • A staged rivalry between wrestlers. 

go to war

verb
  • To enter into an armed conflict. 

  • (of a person) To depart, typically from one's home, to join an army at war. 

How often have the words feud and go to war occurred in a corpus of books? (source: Google Ngram Viewer )